Stress charaterization of thin film materials and fabrication of FPW device = 박막소재의 응력특성 분석과 FPW 소자 제조

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This thesis with the stress characteristics of thin films in chapter 1 and the fabrication of flexural plate wave device in chapter 2. In chapter 1, polysilicon is most frequently used as structural layers in the field of MEMS based on surface micromachining technology and it should have the low stress for the fabrication of free standing microstructures. We suggested a symmetrical stacking method for the preparation of a thick film. In order to minimize the stress and the stress gradient of multi-stacked polysilicon films for the microactuator applications, we investigated the stress behavior in terms of phosphorus distribution and the polysilicon/polysilicon interface at which phosphorus and oxygen atoms were piled up. The phosphorus dopant enhanced the stress relaxation during annealing and also introduced the compressive stress in polysilicon films. The thin oxidized layer formed at the interfaces had the major contribution to formation of the stress gradient of multi-stacked films. The influence of the interface on the stress could be minimized by using the symmetrical stacking of polysilicon films, so that it resulted in the low stress gradient of $-0.15 MPa ㎛^{-1}$/ for 6.5 ㎛ thick film with the stress of -7.6 MPa. The micromachined resonator showed quality factor of 270 and maximum vibrating amplitude of 5 mm under 15 V DC bias and 0.05 V input AC signal in a vacuum chamber at 1 torr. Using the symmetrical stacking process, the thick structural layer with a low stress could be fabricated in the conventional LPCVD equipment which is being used in semiconductor IC technology without any modification. Therefore, this proposed method could be useful in the fabrication of surface micromachined structures. We examined the stress in single crystalline silicon theoretically and experimentally with phosphorus doping level and heat treatment. The dopant atom plays an important role in the formation of stress profile, since dopants located in substitutional sites ...
Advisors
Wee, Dang-MoonresearcherNo, Kwang-Sooresearcher위당문researcher노광수researcher
Description
한국과학기술원 : 재료공학과,
Publisher
한국과학기술원
Issue Date
2000
Identifier
157701/325007 / 000955305
Language
eng
Description

학위논문(박사) - 한국과학기술원 : 재료공학과, 2000.2, [ xiv, 187 p. ]

Keywords

MEMS; FPW; Gyroscope; 응력; 다결정실리콘; 멤스; 박판탄성파; 자이로스코프; Stress; Polysilicon

URI
http://hdl.handle.net/10203/50379
Link
http://library.kaist.ac.kr/search/detail/view.do?bibCtrlNo=157701&flag=dissertation
Appears in Collection
MS-Theses_Ph.D.(박사논문)
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